Composite rotary anode for X-ray tube and process for preparing the composite

Abstract

Methods for the diffusion bonding of a graphite member to a metallic surface as part of a composite rotary anode for an X-ray tube are set forth. The preferred joint for the composite is made by using a layer of palladium in combination with a layer of metal selected from the group consisting of platinum, osmium, rhodium, ruthenium and alloys thereof.

What is claimed is: 
     
       1. In an anode assembly for a rotating anode for an X-ray tube wherein a graphite body is joined to the surface of a metal component of said anode assembly, the metal of said metal component being selected from the group consisting of molybdenum, molybdenum alloys, tungsten and tungsten alloys, the improvement wherein the joint between said graphite body and the surface of said metal component is crack-free and comprises, in sequence, a discontinuous layer of discrete patches of carbide comprising carbide of metal from said metal component metallurgically bonded to said metal component; a first interdiffusion layer comprising metal from said metal component and metal selected from the group consisting of platinum, osmium, rhodium, ruthenium and alloys thereof; said first interdiffusion layer being metallurgically bonded to said carbide patches and to said metal component over areas of contact therewith; a first carbon-barrier layer consisting essentially of metal selected from the group consisting of platinum, osmium, rhodium, ruthenium and alloys thereof; a second interdiffusion layer of metal selected from the group consisting of platinum, osmium, rhodium, ruthenium and alloys thereof and metal selected from the group consisting of palladium and palladium alloys; said second interdiffusion layer being metallurgically bonded to said first carbon-barrier layer and a second carbon-barrier layer consisting essentially of metal selected from the group consisting of palladium and palladium alloys; said second carbon-barrier layer being metallurgically bonded both to said second interdiffusion layer and to said graphite body. 
     
     
       2. The improvement of claim 1 wherein the second carbon-barrier layer has a thickness of about 0.002 inch. 
     
     
       3. The improvement of claim 1 wherein the first carbon-barrier layer is platinum. 
     
     
       4. The improvement of claim 1 wherein the first carbon-barrier layer is platinum--1 wt % chromium alloy. 
     
     
       5. The improvement of claim 1 wherein the metal of the metal component is a molybdenum alloy containing small amounts of titanium and zirconium. 
     
     
       6. The improvement of claim 1 wherein the graphite body is joined to a disc of molybdenum or molybdenum alloy on the underside thereof relative to the anode target of the X-ray anode. 
     
     
       7. The improvement of claim 1 wherein the metal of the metal component is molybdenum. 
     
     
       8. The improvement of claim 1 wherein the metal of the metal component is tungsten. 
     
     
       9. The improvement of claim 1 wherein the graphite body is the disc of the X-ray anode. 
     
     
       10. The improvement of claim 1 wherein the layer of carbide is less than about one micrometer thick. 
     
     
       11. The improvement of claim 1 wherein the metal of the second carbon-barrier layer is palladium. 
     
     
       12. The improvement of claim 1 wherein the metal of the metal component is a tungsten alloy. 
     
     
       13. The improvement of claim 12 wherein the tungsten alloy is tungsten-rhenium alloy.